1. Field of the Invention
This invention relates to residential and commercial heating and cooling systems. More particularly, the invention relates to systems ultilizing geothermal well energy storage.
2. Description of the Prior Art
In the past, earth coupled heat pump systems have proved technically successful, but economically unattractive, as a result of high initial capital requirements and operating costs. Typical systems have traditionally been made up of buried arrays of pipes and some using standard wells. Buried array systems have had limited free surface area and limited access for repair. Both standard type wells and buried array systems have encountered problems with low conductivity in dry soil and reduced transport capacitance following several heating and cooling cycles. It has been demonstrated that earth coupled systems where high ground water exists have functioned better when withdrawing energy from the ground than when storing thermal energy.
Earth coupled systems have been effective in collecting heat from areas with high ground water and inducing freezing around the pipe. This has insured no free space between pipe and ground, and therefore allows conduction as opposed to radiation being the thermal transport mechanism. Attempts to use the earth as a heat sink in warmer environments have been less successful due to drying of the rock around the pipe with the associated reduction in thermal conductivity and the void areas where the pipe has lost physical contact with ground. This is usually introduced by the constant expansion and contraction of pipe with heating and cooling. The temperature changes produce these gaps through the expansion of the pipe, compaction of ground, followed by contraction of the pipe with cooling. If this volume contains only air then thermal transport is very small. While there has been the use of a drip source to attempt the moistening of the surroundings, most systems have been limited to using the earth as a heat source only and therefore increasing the required surface area several orders of magnitude.